The invention relates to a control system for stabilizing the rolling of a vehicle having control elements which are arranged between the wheel carriers or wheel suspension members and the vehicle body and which generate force approximately in a vertical direction, as a function of: the approximately vertical wheel distances to the vehicle body, the lateral acceleration of the vehicle and the vehicle steering-wheel turning angle, to cause a rolling moment at the vehicle body which counteracts rolling motions on the vehicle due to driving conditions.
From DE-OS 28 44 413, a control device of this general type is known. There the stabilizing of the rolling of a vehicle is provided by hydraulically adjustable spring struts to cause a stabilizing moment which, during cornering, is directed against the cornering tilt of the vehicle body. A lateral acceleration measuring device, arranged at the vehicle, emits signals to a controller which interacts with a microprocessor acting as a disturbance-observing device. By means of the controller, electrohydraulic valves are actuated which cause a corresponding oil supply or oil discharge at the hydraulic spring struts. It is particularly disadvantageous that the respective front and rear spring strut is acted upon by the same pressure. For example, during a fast steering of the vehicle, a high abruptly rising transverse force is caused at the front wheel axle which results in swinging motions of the vehicle about the vertical axis. Swinging motions of this type are connected with fluctuating lateral forces and variable slip angles at the vehicle tires so that vehicle handling becomes unstable.
The invention is based on an object of providing a control system for stabilizing the rolling of a vehicle, having control elements which are arranged between the wheel carriers or wheel suspension members and the vehicle body and which generate force approximately in a vertical direction, as a function of: the approximately vertical wheel distances to the vehicle body, the lateral acceleration of the vehicle and the vehicle steering-wheel turning angle, to cause a rolling moment at the vehicle body which counteracts rolling motions on the vehicle due to driving conditions. This stabilizes the rolling and improves the handling of a vehicle.
This object is achieved when the control system is activated only when threshold values of the lateral acceleration and of the steering-wheel turning angle are exceeded and wherein the rolling moment generated by the control elements after activation, as a function of the approximately vertical wheel distances to the vehicle body, is at first formed completely, or for the most part, by the control elements, at the rear wheel axle. Within a transition period (PU),&lt;-&gt;, the activated control system changes the rolling moment distribution between the front wheel axle and the rear wheel axle, to a given fixed rolling moment distribution, &lt;depending on vehicle parameters&gt;. During straight-ahead driving, the control system is not activated and therefore avoids the diminishing of comfort which is caused on an uneven road by means of known systems for stabilizing the rolling of vehicles. If, for example, at the start of a cornering operation, the threshold values for the lateral acceleration and the steering angle are exceeded, a stabilizing rolling moment is at first caused completely, or for the most part, at the rear wheel axle of the vehicle. By means of such a stabilizing rolling moment, the swinging motions of the vehicle about the vertical axis are largely avoided. Within a transition period, determined by vehicle parameters, the stabilizing rolling moment with a given rolling moment distribution is formed by the control elements of the front wheel axle and of the rear wheel axle. The control system with the variable rolling moment distribution, advantageously improves the roll steer effect of the vehicle and the driving safety by reducing the dynamic wheel load fluctuations during cornering and on an uneven road.
Other advantages are obtained when the vehicle parameters utilize the yaw velocity of the vehicle and the approximately vertical wheel compression speeds or the steering-wheel angle speed.
It is also advantageous if the control elements, after the activation of the control system, maintain the rolling moment distribution between the front wheel axle and the rear wheel axle until the absolute value of the steering angle speed reaches a low value. Also, changes of the rolling moment distribution are carried out in the transition period in such a manner that the rolling moment part generated by the control elements at the vehicle rear wheel axle will decrease and the rolling moment part generated by the control elements at the vehicle front wheel axle will increase. The length of the transition period takes place as a function of the yaw velocity of the vehicle and any one of an approximately vertical wheel compression speeds and a steering-wheel angle speed.
Also during the transition period, the change of the rolling moment distribution, starting from a reverse time (U) is carried out in such a manner that, until the preset rolling moment distribution is reached, the rolling moment part generated by the control at the vehicle rear axle will increase and the rolling moment part generated by the control at the vehicle front wheel axle will decrease.
It is also advantageous if the magnitude of the rolling moment generated by the control elements is also dependent on the steering wheel turning angle and the approximately vertical wheel compression speeds.
It is also desirable if dampers are arranged between the wheel carriers, or the wheel suspension members, and the vehicle body and if they have their damping force increased when the control system is activated.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.